Summary unit 13: Learning aim B oxidation-reduction reactions in order to understand their many applications in analysis
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Course
Unit 13 - Applications of Inorganic Chemistry
Institution
PEARSON (PEARSON)
Your assignment covers a wide range of topics related to oxidation-reduction reactions, including displacement reactions, electrochemical cells, oxidation numbers, and titrimetric methods. It provides detailed explanations and applications in analysis, demonstrating a strong understanding of the co...
Oxidation of an Aldehyde with Acidified Potassium Dichromate solution
In alkaline and acidic conditions, the
aldehydes react differently. This is because
aldehyde is converted to a carboxylic acid
when it's oxidised in acidic conditions
using potassium dichromate solution.
Nevertheless, the aldehyde undergoes a
different reaction since the reaction
mixture contains hydroxide ions. This
indicate that Instead of forming a
carboxylic acid, the mixture of the
aldehyde and alkali produces
salt.(Chemistry LibreTexts, 2013)
Method:
Firstly, rinse the equipments and making sure that its
dry. Next, add small amount of acidified potassium
dichromate solution into the test tube, follow by few
drops of aldehyde. Then, warm the mixture gently for
few minute by using bunsen burner of hot plate. Lastly,
mix the solution using glass stirring rod and record and
evaluate the observation.
Observation:
Therefore, the dichromate ion is reduced since it has gained 6 electrons as well as 14 hydrogen ions
in order to form two chromium ions and seven water molecules. This means that the orange
dichromate ion(VI) is reduced to green chromium ion (III) by the aldehyde. As a result, the aldehyde
is oxidised into carboxylic acid. This indicates that the orange colour of potassium dichromate
solution will turn green when aldehyde is added. Moreover, gases including carbon dioxide as well as
sulphur dioxide may be produced during the experiment which is also based on the type of aldehyde
that is being oxidised. This further suggests that It is possible to observe the gas bubbles rising from
the solution, which shows a chemical reaction is occurring. In addition, The temperature of the test
tube could fluctuate during the experiment. This implies that heat is emitted throughout the
oxidation process because it indicates that the reaction is exothermic. (Chemguide.co.uk, 2015)
, Evaluation
Titration is commonly used in the industry, particularly in the pharmaceutical industry, for a variety
of purposes. As a result, I will describe each approach in detail, as well as the benefits and drawbacks
of each method, and assess four analytical techniques extensively employed in industry, such as:
iodine/thiosulfate titration to determine the concentration of Cu2+, iodine/thiosulfate titration to
determine the peroxide value of fats and oils, iodine/thiosulfate titration to determine the ClO-
concentration in bleach, and dichromate(VI) titration to determine chemical oxygen demand.
● Iodine / thiosulfate titration to determine the concentration of Cu2+
The iodine/thiosulfate titration method for determining the concentration of Cu2+ is a type of
analytical technique which is widely used in a variety of industries, including water treatment,
agriculture and food science. This suggests that the method depends on a redox reaction between
Cu2+ and iodine when there is an excess of the iodide ion, which is followed by thiosulfate titration.
Therefore, there are some advantages of the iodine/thiosulfate titration method such as: the
method can be performed in order to determine the concentration of Cu2+ ions in aqueous solution
which means that this method is straightforward & easy to carry out. Another advantage is that the
method can be able to detect low concentration of Cu2+ and the reagents used are both
cost-effective and easily accessible. On the other hand, the disadvantage of iodine/thiosulfate
titration method is that some substance in the sample can be able to interfere with the reaction,
which means that it could lead to inaccurate results. In addition, since the method involves using
iodine solution which can be toxic, which is possible that accidents occur and could cause skin & eye
irritation. An additional drawback of the procedure is that it takes a long time, and the colour
changes could not be visible, which could result in a mistake when determining the endpoint.
Moreover, alternative methods such as spectrophotometric and Beer-Lambert’s law can be used to
determine the concentration of substance (Cu2+). This is so that they can offer accurate and
trustworthy results since they are extremely extremely specific. These techniques are therefore
commonly used in industrial settings where more precision and efficiency are essential. (Study
Mind, 2023)
● Iodine thiosulfate titration to determine the peroxide value of fats and oils
The iodine/thiosulfate titration method is commonly used in order to determine the peroxide value
of fats and oils. This is due to the fact that the method includes the oxidation of iodide ions by
sample-based peroxides, which is followed by a thiosulfate titration to measure the peroxide value.
As a result, the method is widely used in pharmaceutical industries, food industry, animal feed
industry. The primary advantage of this method is that it makes it possible to accurately determine
the peroxide value. As a result, a variety of fats and oils may be used with the procedure, making it
suitable to use with various sample types. Another benefit is that the regents are very affordable,
making them easily accessible. Nevertheless, the method's drawback is that determining the
endpoint using an indicator may sometimes contribute a level of inaccuracy into the results, which
might result in obtaining wrong results. Additionally, it is likely for contamination to happen
throughout the method, and certain substances may be able to interfere with the reaction, which
might have an impact on the peroxide value determination's accuracy. Additionally, other alternative
methods such as the peroxide value test technique (POV) and AOCS are two other methods that
may be used to determine the peroxide value in oils and fats. (York.ac.uk, 2023)
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